1. Field of the Invention
This invention relates to a detecting apparatus for detecting a reinforcing strip of film applied to a slide fastener and more particularly to such an apparatus which is capable of detecting the presence and position of a reinforcing strip on a continuous chain of slide fasteners during the course of manufacture thereof.
2. Prior Art
There are known various types and forms of slide fastener, one of which is a so-called separable slide fastener equipped with a separable pin and box member at that end portion of the fastener which is reinforced as by fusion of a strip of a thermoplastic film to provide sufficient rigidity to withstand repeated manipulation of the separator. The reinforced end portion is notched for mounting the separator, and the fastener chain thus assembled is then cut into individual product lengths. However, in the event of failure to attach the film strips or misalignment thereof relative to the fastener, the result would be a defective slide fastener product.
It has been proposed in the art to detect the presence of the reinforcing strip on the fastener chain by sensing the thickness differential of the fastener tape, the thickness of the tape portion at which the strip is attached being greater than that of the tape web. However, this method of detection is not wholly satisfactory because of the aforesaid thickness differential being so small that the detection, if not impossible, would be often subject to error or malfunction. Attempts to eliminate such malfunction would involve expensive, high-precision, structurally complicated detecting devices.